Filtration material may be incorporated within any number of different types of filters and/or may be formed or otherwise constructed into filtration devices. In any case, it may be desirable to attach a component element to the filtration material in order to facilitate the incorporation of the filtration material with other elements or in constructing the filter material as a filtration device. Filtration material itself typically comprises a media capable of permitting fluid flow through the media but defining orifices or passages through the media which limit the passage of particulate matter or the like through the filter media. Such media may otherwise be designed for removing any constituent component of a fluid from the fluid as it passes through the filtration media instead of or in addition to particulate removal (i.e. by attraction or chemical reaction).
The present invention was developed, in particular, for the production of respiratory masks that are utilized in a wide variety of applications for protecting a user's respiratory system from contaminates and/or unpleasant or obnoxious gases within the air. Moreover, medical care providers utilize such respiratory masks for preventing the spread of harmful microorganisms either to or from the provider.
Various forms of respiratory mask are commercially available; some of which are categorized as “disposable” because they are intended to be used for relatively short periods of time. Other non-disposable respiratory masks may include replaceable filters even though the masks themselves are reusable. Disposable masks typically have a mask body that is formed predominantly from an air filtration material and that is shaped or configurable to fit over at least the nose and mouth of a person. Replacement filters for non-disposable masks typically include a layer of air filtration material along with certain structural components whereby the filter is connectable with the reusable mask.
Disposable respiratory masks can be generally classified into one of several categories, some of which are noted as follows: 1) flexible flat masks that are sometimes folded or pleated and that are sized to fit relatively flatly over a person's nose and mouth; 2) foldable masks that can be folded in a flat state and unfolded into a cup-like usable state where it can fit over a person's nose and mouth and; 3) molded masks that are pre-shaped into their usable state. Of these, either type of the fold-flat masks can be packed flat and may be provided with appropriate seams, pleats and/or folds to accommodate usage. The foldable type masks that can be unfolded into a cup-like state are usually formed with panels that are defined by seams, pleats and/or folds that enable the mask to be opened into the generally cup-shaped configuration. Molded masks, on the other hand, are pre-formed into a desired face-fitting configuration and generally retain that configuration during use. When a fold-flat or molded mask is in use, the mask body forms a breathing zone to at least some degree around at least the nose and mouth of the wearer. Air is drawn into the breathing zone through the air filtration material when the wearer inhales.
Disposable respiratory masks generally incorporate at least one attached component that is attached to or through a layer of filtration material or composite material having a layer of filtration material. For example, almost all such masks include a headband, ties or other means by which the mask can be secured to the user's head. Furthermore, such masks also are known to incorporate other attached components including valves, nose clips and face shields.
Some methods that are frequently employed for attaching such components are based upon the use of thermal welding or ultrasonic welding, such as described, for example, in U.S. Pat. No. 5,325,893. These methods are advantageous in that they can attach such a component in a way such that the component is effectively sealed with the filtration material. That is, because the welding can be done all the way around the component, the filtration material, which is likely a fibrous material, can be thermoplastically welded with itself and the component. Thus, the component can be sealed to the filtration material so that the filtering affect of the filtration material is not compromised at the attachment interface. However, welding techniques are generally more costly and complex than others in that they require the provision of relatively complex equipment for conducting the ultrasonic or thermal process, and, especially where fibrous material is connected with a component, requires a sufficient control system to make sure that a good attachment results.
Alternatively, for some components and other forms of respirators, adhesive bonding is known to be used. The benefit of adhesive bonding is that, like welding, an effective attachment can be more easily provided. That is, as long as the adhesive is compatible with both the filtration material and the component, it can be applied all the way about the component to create a good attachment. The seal created by the attachment, however, is enhanced only where the adhesive is applied. That is, an external layer (which may be filtration material or otherwise) may be attached and sealed with the component by the adhesive, but other layers may not be sealed with one another, the external layer, or the component. As such, a good seal (i.e. one that doesn't permit larger particles to pass than is the function of the filter, for example) may be compromised. In any case, such an adhesive attachment technique requires the added expense of the adhesive and further requires the provision of a means to dispense and control the application of the adhesive. This adds cost and complexity.
In other situations, mechanical clamping techniques are also known, including the use of fasteners like staples or other clamping structure. Such mechanical systems have the general advantage that they do not require complex bonding equipment such as thermal and/or ultrasonic generators and controls or adhesive dispensing and applying devices and controls. However, a mechanical clamping system itself may require complex alignment and control mechanisms. Examples of mechanical attachment techniques are disclosed in U.S. Pat. Nos. 5,374,458 and 5,080,094 and in published international applications WO 96/11594 and 96/28217. The biggest concern when utilizing a mechanical fastener or clamping system is the creation of an effective seal, i.e. one that will not permit a significant quantity of any contaminant to pass that is otherwise intended to be excluded by the filtration material to which the component is attached. This problem may vary depending on where on the mask, for example, the component is attached (such as, for example, directly in front of the user's nose as contrasted with a point off to the side). Moreover, certain mechanical clamping methods may not only require the provision of an additional fastening component, but also may also require additional alignment and fastener or clamp manipulation steps.
These attachment methods are also employed in other fields when it is necessary to secure components to fluid filtration material, for example in the manufacture of air filters, such as vacuum cleaner bags, and oil filters. An example of a mechanical clamping technique used outside the field of fluid filtration is disclosed in U.S. Pat. Nos. 4,909,434; 5,125,886 and 5,199,635 where mechanical clamping is used to secure a pour spout to a liquid container (in some cases in combination with heat sealing).